Fiji police want to determine whether the military commander, Commodore Frank Bainimarama, committed treason by his actions after the May 2000 coup.
Radio Fiji reports that this follows a complaint to the police by the president of the Fiji Citizens Freedom Movement, James Bachu.
Mr Bachu is alleging that Commodore Bainimarama committed treason when he asked the former president, Ratu Sir Kamisese Mara, to step down to allow the military to take control of the country during the political turmoil.
The assistant commissioner of police, Moses Driver, says they are working to establish whether Mr Bachu's allegations have any substance.
This contradicts a police statement last month, which said Mr Bachu's complaint was not a police matter.
Mr Driver now says detectives will research the allegations for concrete evidence before launching a substantive investigation.
This includes a study of the court judgements relating to the coup and a statement from Mr Bachu.
Mr Driver says police will only talk to Commodore Frank Bainimarama if there is evidence of the allegations against him.